Doctor
by MiyuTanemura
Summary: An accident during a mission has an unexpected side-effect. Gray/Natsu. PWP, crack, bad!fic, AU. Dedicated to Cristallina.
1. First

**Disclaimer:** I don't own anything. Heck, I don't even know how to write this properly!

 **A/N1:** My dear Cristallina, I'm so sorry that the first thing I write for you is this… nonsensical stuff. Sorry!

 **Warning:** Bad!fic, crack!fic, dub-con, anal sex, au, healing cock trope.

* * *

 **Doctor**

Fiore is a land of magic. There is the usual magic, used by mages and their guilds but, a good part of it has been forgotten – the roots of magic.

Every now and then ancient traps or books would unleash ancient magic and the results could be quite hilarious, sometimes.

In Magnolia, where the very well-known Fairy Tail guild resides, quite a bit of the mages have already encountered ancient magic. Thankfully, the results of such encounters weren't overly bad but there was one case that got quite well-know, much to the embarrassment of the two mages.

One day, team Natsu was following a group of fugitives through some ruins. At one point, during the mad run, Gray fell inside a hole that suddenly opened underneath his feet.

The ice mage fell down on it and on top of a strangely plush pillow, filled with purple tendrils that started wriggling over Gray's body. The ice mage attempted to get up, push the tendrils away from his body but the more he moved, the tighter and longer they became, their appearance glossy and semi-transparent.

His yelling had one form appearing at the mouth of the hole. When Gray looked up, he saw Natsu who was looking strangely at him and his predicament.

"What the fuck are you waiting for, flame-brain? Do something!" he all but yelled.

That seemed to make Natsu snap out of whichever trance that had gotten over him. The pink haired mage jumped inside the whole and hurried towards Gray.

But by the time he got there, the tendrils had converged to Gray's crotch and splashed over there, making the area become tingly. And then as soon as Natsu was nearby, one small bit rose from it and splashed Natsu in the face. The fire mage sputtered and tried to clean the weird fluid but he didn't get to do anything as it suddenly evaporated. What liquid was also in Gray's body followed the same path and the ice mage found himself laying in a slab of stone.

"What the fuck was that?" Natsu asked, confused.

"How do I know?" Gray retorted, as he got up and brushed himself off.

They heard the girls calling for them and headed towards them, not paying much mind to the strange event that had just happened.

It wouldn't be until much later that they would see the results of that…

* * *

"How can you be so dumb?" Gray yelled at Natsu, the Salamander's form strewn over one of the beds at the infirmary while Wendy worked as hard as possible to heal her friend. Strangely, none of her efforts were being fruitful.

"I don't understand. This should be getting better but it's _not_!" she said worriedly while trying to staunch the blood flowing. It didn't make sense that Natsu's own usual healing wasn't kicking in. The blue-haired mage was extremely worried.

"What can we do?" Lucy asked, approaching Wendy, interlaced hands trembling slightly.

"I don't know." The aforementioned mage shook her head and looked at their prone friend.

"I don't believe it." Gray grumbled. "Come on, snap out of it, Natsu!" he all but yelled, placing one hand on the fire mage's arm, trying to rouse some reaction from him.

Unbeknownst to him, a faint purple coloured mist started emerging from their point of contact. Wendy noticed it, her eyes opening wider, and she stared, waiting to see what might happen next. The mist started moving, small filaments started to head towards Gray's crotch area and remained there, hovering and the more solid bits clinging to the fabric of Gray's trousers.

"Hm… Gray…" Wendy finally said, making the ice mage look at her, one eyebrow arched. "I mean… can everybody leave except Gray?" she looked around at the surprised expressions of Erza, Lucy, Happy and Carla. After a beat, there were nods and the remaining people left the room. Wendy started twisting her hands as she looked everywhere but at Gray. It was clear that he hadn't noticed it yet. She cleared her throat and finally looked at him. "Has anything happened, Gray?"

"Huh? What do you mean?" Gray blinked, confused.

"During one of the previous missions or so. That mist there isn't usual." She waved in the ice mage's direction, making him look down.

"What the-!" Gray asked, noticing the coloured air in front of himself. "It wasn't here before!" He said as he tried to dissipate it, only making it cling to his hand, small tendrils starting to curl around the limb.

"No, it wasn't. But from the moment that you touched Natsu it appeared." She said pensively. "I don't know what that means Gray but Natsu did seem to breathe a little better during the moment you two touched. This is super weird but… I think that you might be the cure for Natsu."

"What the-? Me, cure?" Gray asked, mouth hanging slightly open. "What do you mean?"

"Apparently, your touch is what can heal Natsu." She motioned for him to place his hand on Natsu's shoulder. As Gray did it, a pale, lilac light covered the area, mending the skin nearby.

The ice mage removed his hand as if it had been scalded.

"What the fuck is this?" he asked, wide eyed.

"I don't know. I'll have to as Levi and do some research. But it seems that the more…" at that she definitely coughed and shifted her gaze to the light blanket covering Natsu, "…intimate you are with him, the better the results."

"…" Gray stood, blinking slowly. When the meaning of the smaller mage really hit him Gray's mouth fell. "You can't be saying what I think you are!" he all but yelled.

"Sorry…" she said softly, face red as a cherry. "But you guessed correctly."

"You've got to be kidding me. Wendy. It's not like I can't or…" he paused abruptly to shake his head. "I can't do anything because I don't have Natsu's consent." He pointed at the prone mage.

"But Gray… if _you_ don't do anything, he'll die." She looked at the pink haired mage, noticing how the usually gold-tinted skin was becoming of an ashy tone while the bandages covering him were becoming redder. "I know that you guys were… and then… but…"

With a long-suffering sigh, the ice mage raised his hand, a sign for her to stop.

"Alright. I'll see to it. I'll do my best to make Natsu get better. Now, it might be best for you to leave the room and don't let anyone enter before I say something, alright?"

With a timid nod the smaller mage left the room, the soft click of the door sounding definite on Gray's ears.

"What am I supposed to do with you?" Gray asked the room at large, knowing that he wouldn't have a reply. He looked down at his waist and the small mist seemed to have grown and become more attached to both him and Natsu, almost as if trying to join together two pieces. With movements so practiced that they didn't need any conscious thought – not that it had had for a long time – Gray kicked off his boots and slid down his trousers and underwear. Then he pushed the blanket back, noticing that Natsu only had his underwear, which he removed quickly. Then he sat on Natsu's thighs.

The purple mist seemed to start to spread out over Natsu's form, making the frown that was creasing his brow smooth out slowly. He held both of Natsu's hands, seeing the gold seeping back into his fingers, bruised knuckles slowly clearing as the skin mended itself. Gray ran his hands over Natsu's arms, going up to his shoulders and down the planes of his chest. The movement of said chest had been slightly more irregular but now, under Gray's hands seemed to become deeper, more normal. The ice mage leaned forward, his left hand coming to the small space beside Natsu's right shoulder to let him brace himself. He left his lips brush against Natsu's bruised face, seeing as wherever he touched smoothed out, until Natsu's previous rictus became calm, the same he wore whenever he was in deep slumber.

Without wanting to believe his eyes, Gray came to the ground once again, not wanting to believe that his mere touch had brought colour to Natsu's complexion. However, there was still blood flowing – he could smell the metallic tinge of it – and that meant that another stage of intimacy was wanted. He curled one of Natsu's hands over his erection and started stroking. The lax hand slid slowly over him and since it was going dry, it wasn't being overly pleasurable for Gray. The ice mage quickly placed the hand back on the cot before going to the bedside table, there were a few jars of ointment but Gray caught the scent of one that didn't seem too bad – the slight scent of peaches on a jar that contained a viscous pinkish-golden fluid – so he brought it with himself. He turned Natsu's palm upwards and let some of the fluid fall on it. Then he resumed his previous occupation, Natsu's hand curled around himself. Natsu's lips parted in a sigh but the blood, while apparently having slowed down, hadn't stopped yet.

"Okay then, here goes nothing." Gray climbed into the bed and placed himself between Natsu's legs, parting them so that they were thrown over both sides of himself, the way unimpeded. "This really isn't how it was supposed to go, but you had to go and do a mess of things, right, Natsu?" Gray spoke softly as he ran his hands over the fire mage's thighs, he rubbed at them, the motion denoting some anxiety. Then, with a final sigh, he grabbed the jar and let some of the fluid drip down his fingers, slicking them. By the corner of his eye he could notice the fine mist becoming thinner but concentrating in the small space between them. Gray's slick hand headed towards Natsu's entrance, which made the mist appear to shine in some places.

The fire mage's body was pliant, strangely gave way and the lubrication seemed to stick right on the first motion.

Gray coated his own erection while trying not to be weirded out by the purple tone of the mist that adhered to it, nor the way it seemed to scintillate.

The ice mage placed one pillow under Natsu' hips before settling back on his haunches once again.

And then there wasn't anything else for him to do to procrastinate.

With a sigh, Gray threw one of Natsu's legs over his shoulder and then lined himself up and started pressing inside.

As soon as the head of Gray's erection popped inside, Gray heard Natsu let out a sigh. When he looked up, the fire mage's mouth was parted and there seemed to be a bit of movement under his lids.

Gray continued to press inside until he bottomed out.

There was a noise coming from Natsu's throat and so Gray took it as a good sign and pulled back, only to plunge back in again. His hips started to pick up speed and before long Gray was fucking Natsu in earnest.

The strangest thing, though, was to see that his actions did have an effect on the fire mage.

Slowly, the bruises and cuts were disappearing. Blood no longer flowed and, while slowing down to a gentle rocking right against Natsu's prostate, Gray pushed back one of the large bandages from his stomach and could see the skin knitting itself, becoming pink before the gash disappeared, only leaving golden skin behind.

Gray bit on his lip and adjusted Natsu's position, curling his legs around his own waist. Now he had a better grip.

He could feel himself start to have a tightening on his lower stomach and so he knew that he was close. A quick grope showed him that Natsu was also reaching the brink himself. Gray pounded away and then, like the snap of a coiled rope, Natsu's back arched and he came all over his stomach and chest.

His eyes opened.

Gray tilted his head down and thrust a few time more before he was coming, emptying himself inside the fire mage.

The next thing he knew, Natsu was speaking.

"What the fuck's going on?" he asked in a surprised voice before he started squirming and working on distancing himself from the ice mage. He grimaced when he dislodged the erection and felt liquid seeping from inside.

He looked up at Gray, demanding an explanation.

"It was the only way, okay?" Gray said as he started raking a hand through his hair, only to notice that it was the slicked one. He paused and made a face at it. "You were in a bad shape and nothing that Wendy did worked."

"And from that to _this_ , how did it go? I never had trouble with getting better on my own." Natsu countered.

"It wasn't working. You were in an unusual bad shape. But then Wendy saw the air and she told me that I could help you." He heaved a sigh. "Was the only one who could help you." Gray said the last words in an odd tone. Natsu caught it.

"And why's that, huh?" he inquired.

"I don't have a clue. Except… she asked if something had happened during a mission and I just remembered. Do you remember when I fell down that hole in… Rotun, was it? That's the last time I remember something slightly weird happening. At least, more unusual."

Natsu mused over his words before nodding.

"Yeah, I remember it. You fell down a hole and there was something weird, dusty, in there. But what does that have to do with me?"

"You'd have to ask Wendy. She said she was going to do some research with Levi." Gray shrugged as he stood and located his clothes.

"I don't know if I should believe you. I do remember being in some pain but now I'm completely… fine, normal. As if there hadn't happened anything." Natsu sat up and started peeling off the bloodied bandages, frowning. "You're really telling the truth, aren't you?" he breathed out. "This was all mine?"

"Yup." Gray nodded as he came to stand beside the bed.

"And… what? You fucking me was what healed me?" he turned at Gray.

"It would seem so." Gray acquiesced as he looked at the unblemished golden skin. There was no trace of gashes or anything. It was as good as new.

While in his musings, Gray didn't see Natsu's hand curling into a fist or how he swung it at him.

Gray was punched and thrown into the nearby cot.

"The fuck!" he yelled, glaring at Natsu.

"That's in reacting to doing that to me while I was unconscious." Natsu grumbled as he hopped off the bed and approached Gray, he extended his hand. "But, thanks. It looks like I wouldn't still be here if it weren't for you. _But_ we're going to have a serious talk about what happened here. You _don't do_ that."

"I know." Gray nodded seriously. "And I knew that it was wrong but it was the only chance. The blood-"

"Okay." Natsu cut Gray's tirade. "You know it was wrong, you saved me and now we better see this through." He grimaced as come slid down his leg. "But maybe after a shower."

Gray snorted.

* * *

 **A/N2:** Huuuh… don't mind me. Apparently I'm having some strong Gray/Natsu feelings right now. It's Cristallina's fault, anyway. That and some RL not so funny things. Oh well…

But, yeah, don't look for plot or anything of the sorts. This is intentional bad!fic and so it has a lot of nonsense. In the end, this is just a PWP. With more snippets to come. Some more filthy than others but still in the same tone. I don't even know.

Do heed the warnings. Things are going to get "worse"… OTL

Story's unbetaed.

Feedback's always awesome! Feel free to leave some ideas. xD


	2. Second

**Warnings:** self-lubrication, riding, anal sex.

* * *

Quite a while had passed since that first time and now Natsu and Gray were closer than ever. They still fought and the bickering reached heavenly levels but normalcy had returned to the guild. Somewhat. (Of course that not everything had run completely smoothly. Juvia had been a bit of a problem… but now the rain mage had calmed and only threw glares at Natsu every now and then for stealing her Gray-sama.)

Natsu and Gray were entering the guild, arguing, while Lucy, Erza and Happy came behind with amused expressions.

"You can't be so reckless all the time! It's true that you have an abnormal resistance but, can you not be thrown into all the boulders in existence?" Gray said, throwing his hands up.

"Reckless? I wasn't the only one who threw that guy over the cliff and nearly fell there myself, was I? You should look before going, too." Natsu countered with a glare.

"Oh, fuck you! Who's in worse shape, hm?"

"You're not in perfect shape, asshole! I can see you limping."

"But I don't have my ribs broken!"

They continued arguing while they headed towards the rooms, under their guildmates' amused – and sometimes lecherous – and in one case, jealous, looks.

* * *

As they finally got inside the room they quickly disrobed and Gray went to sit on the bed.

"Okay. How do you want to do this?" he asked, motioning Natsu to approach.

"Pfff, you ask as if you didn't know the answer." Natsu replied as he stood in front of Gray. The mist spreading out between them.

Gray's hands curved around Natsu's muscled buttocks, two fingers slipping inside the crease and locating the fire mage's entrance. He plunged both fingers inside, assessing the amount of lubrication within. Natsu gasped.

"You perv'." He teased as Gray started thrusting his fingers, squelching noises coming from within. "I'll ride you, of course."

"Mmm…" Gray agreed in a non-committal way as he eyed Natsu's erection. He leaned forward and popped the head in his mouth, eliciting a surprised noise from the fire mage while two hands instantly pressed against his shoulders, searching a leverage of sorts.

"You fucking…" Natsu grumbled once the unexpected feeling abated. He glared at the ice mage.

Gray released Natsu and looked up with a pleased smile. Natsu rolled his eyes and crushed his mouth against the other mage's one, trying to assess his dominance but falling short due to the pain. He gasped and Gray plunged his tongue into Natsu's mouth, gentle hands cradling his sides as his tongue toyed with Natsu's, while Gray sucked Natsu's tongue to his own mouth, the kiss becoming overly sloppy for a few moments. And then he let go.

"Alright then. Let's do it." Gray said as he scooted back in the bed until he was leaning against the headboard, legs stretched out in front of him. Natsu followed suit, though at a slower pace. He straddled Gray, holding onto the wood of the headboard. And then Gray started direction him, one hand on the fire mage's hip while the other held onto his erection.

Natsu let out a gasp as the head penetrated him, the first intrusion was always the bad part, but then took the matter into his own hands and impaled himself in the rest of Gray's prick in one quick movement.

That had both mages groaning in unison. Natsu leaning his forehead against Gray's.

"You dumbass." Gray chided hoarsely as he ran his fingers around the area where they were joined. "That can't have been good." He half glared at Natsu as he slid his index fingers inside, stretching the rim a little more and in reaction Natsu's hips tilted upwards, his erection sliding against Gray's stomach, already slick with quite a few spurts of pre-come.

"Shut up." Natsu said in a breathy voice. "If I'm to wait for you, I won't be healed next week."

"Impatient as always…" Gray said long-sufferingly.

"Nah, you're just too slow." Natsu smiled smugly. "And I can take more, if that's what you want…" he arched an eyebrow.

"Nope." Gray said as he removed his finger. "But one day you'll take my hand." He got a breathy laugh in response. "Though, for now, you do all the work." He said teasingly as he gave a small slap on Natsu's rump.

"So lazy. As usual." Natsu said as he started moving. He raised slowly before letting himself fall down, every now and then he would pause to move his hips in a slow circle, teasing. And then, he picked up a rhythm and was happily riding Gray. The ice mage also helped, thrusting up in counterpoint with Natsu and holding tightly against his hips.

Not many words were exchanged, just grunts and laughs and the odd kiss. When Gray brushed against the fire mage's prostate the reaction made Natsu's muscles freeze, his head tilt back as he let out a " _hell yes!_ ".

After that, it was a race towards completion. Natsu, who was being stimulated in both ends, couldn't hold it so he came just moments before Gray who bit down _hard_ at the fire mage's shoulder.

Gray leaned his head back and saw the bite disappear right before his eyes, washed out by the scintillating must that enveloped them.

"Whew." Natsu said as he looked at Gray, the ice mage's erection still lodged inside himself. "That was a good one. I'm as good as new." He shot Gray his trademark grin.

"See if you don't get too mangled next time, okay?" Gray shot back teasingly. Absentmindedly he was touching Natsu's rim, the tips of his fingers seemingly searching for the fluid plugged inside.

"Oh, yeah!" Natsu said suddenly. "Oi! What's that you were saying about your fist?"

"What? Don't think I could do it?" Gray shot back.

"No, you can do it, ice-perv'. I just don't know if I would like that." The fire mage scrunched up his brows.

"I'd make you like it. Promise." Gray leaned forward to peck at the shoulder he'd bitten. "May I?"

"Huh. What? And second, where did that biting thing come from? I think you're leaning some things, heh?"

"Shut up." Gray laughed but he also took that moment of inattention to slip his index and middle fingers inside Natsu, feeling the slightly loosened muscle give and come start sliding down his fingers and hand.

Natsu shot up, hips bucking slightly in reaction. However, it wasn't for long because Gray took his fingers back and then helped the fire mage rise himself and flop down on the bed on his side.

"You know what? You've become quite a pervert." He breathed out.

"You say that as if you didn't love it."

Natsu didn't reply. Just rolled his eyes.

* * *

 **A/N:** A new chapter. I'd planned to post it earlier but had some health troubles. Thankfully things are getting better. Yay.

Huh, this is just a big PWP for me to write down my Gray/Natsu feelings. And to entertain Cristallina a bit. What can I say, I'm in a giving mood. xD

Unbetaed.

Feedback would be nice.


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